The general manufacture of integrated circuit (IC) chips has been practiced for many years. The successful IC manufacture is often dependent on the ability to create regions of differing composition within the semiconductor wafer used as the substrate for the integrated circuit or within structures deposited on the wafer. The performance of these regions is often dependent on the degree of difference in composition. Thus, the function of a region may vary depending on its composition (e.g. concentration of dopant) and the composition of the regions surrounding it.
The continued demand for more compact and more detailed circuit designs in the integrated circuit industries often demands improved ability to create compositional differences having very tight tolerances (compositional and/or dimensional). One design structure that has presented these demands is the so-called trench capacitor.
Trench capacitor structures usually comprise a trench in a semiconductor substrate (usually silicon). Immediately below the trench wall, the substrate is doped to increase its charge storage capacity to form one plate of the capacitor. Typically, the dopant (e.g. As) is put into place by diffusion or ion implantation. At the trench wall, a dielectric layer is formed to serve as the node dielectric of the capacitor. The trench is then filled with a conductive material (typically doped polycrystalline silicon) which becomes the second plate of the capacitor. The doped region below the node dielectric is often called the "buried plate" of the capacitor.
One advantage of the trench capacitor design is that it takes up less area relative to the principle plane of the substrate. Even with this inherent design advantage, there is a further demand to conserve space on the chip by placing the capacitors closer together. If the trench capacitors are placed too closely together, unwanted interactions may occur between the doped regions which form the buried plates of the adjacent capacitors. On the other hand, it is generally desired to have a high level of dopant in the buried plate so as to ensure good capacitor performance.
Conventional techniques have generally resulted in a trade-off. Where high doping was achieved, the size of the doped region increased such that close placement of the capacitors was impossible without unwanted interactions. Control of the size of the doped region has generally required the use of reduced dopant levels and worse performance. Thus, improved doping methods are needed for forming doped regions useful as buried plates in trench capacitors and other devices. Further, there is a need for trench capacitors having buried plates of high charge storage capacity and tight geometrical configuration. The need for high dopant levels in tight geometries may also be present in the fabrication of other integrated circuit components.